The metal used in fireworks since it burns with a dazzling white light is -

The correct option is D

magnesium.

The explanation for the correct option -

• Elements that have an excess of electrons and a tendency to donate them are generally considered metals. For example - Sodium$\left(\mathrm{Na}\right)$, Silver$\left(\mathrm{Ag}\right)$, etc.
• Magnesium is metal with silvery-white color.
• It is a very reactive metal and when exposed to air, it reacts with Oxygen producing a dazzling white flame.

The explanation for the incorrect options -

• Option A is incorrect because Zinc is metal with bluish-white color. When burnt in the oxygen it gives fumes of Zinc oxide $\left(\mathrm{ZnO}\right)$that are of bright bluish-green color.
• Option B is incorrect because Calcium is the silvery-white colored metal that burns slowly with Oxygen to give the yellow-colored compound Calcium Oxide $\left(\mathrm{CaO}\right)$.
• Option C is incorrect because Mercury is a silver-colored liquid at room temperature. Under ordinary conditions, Mercury does not react with air.

Hence, Option D is the correct answer.